This invention is directed to a circular coupling system of the type for joining a tubular member, such as a pipe, to a second member, which may be a pipe of a different diameter, or a precast concrete manhole, for example.
There is a growing concern today for a greater protection of the environment. This is evident by the imposition of numerous laws and regulations dealing with the air and clean water. The EPA is looking into the infiltration/exfiltration (I/E) rates of our nations's sewer systems. The United States has millions of miles of sound sewer pipe jointed with cement mortar or asphalt that shrinks or cracks. This and other defects allow excessive infiltration into the system, causing problems in the treatment of sewage or exfiltration in close proximity to water supply lines and streams, both I/E become a threat to the quality of our water supply.
U.S. Pat. No. 4,927,189, to the inventor hereof, the first of a series of patents directed to an internal expansion coupling, in its preferred embodiment, is directed to a coupling system for use in joining together a pair of pipes aligned in end-to-end relationship. The coupling thereof includes an elongated open ended tubular member formed of a relatively rigid sheet-like member, such as steel sheet, where the sheet ends overlap such that the end portions lie contiguous with each other. A continuous sleeve, formed of an elastomeric material, overlaps the sheet side about at least one open end of the tubular member. The sleeve, about the circumference thereof, is provided with at least one continuous upstanding rib, which is adapted to lie adjacent to and be compressed against the inside wall of a pipe. Finally, means are provided for expanding the sheet-like member whereby the sheet ends move circumferentially towards one another urging the elastomeric sleeve and the rib against the inside wall of the pipe. The added pressure from the flowing medium therethrough only serves to enhance the coupling joint.
While the invention of '189 represented an effective approach to joining two aligned pipes with essentially the same diameter, a need continues for a coupling system which can be adapted to join pipes of different diameters, and to a system which can join a pipe to a designated hole in a concrete manhole, for example.
U.S. Pat. No. 5,261,761, to Knappert et al., teaches a manhole adapter, formed of a resin (ABS). The ABS material is formed into a coupling-collar, by creating a cylindrical body having an outside diameter surface structure formed into multiple adjacent rib-grooves, which subsequently receive portions of grout to create a strong bond between the grout and the ABS manhole adapter. Additionally, the cylindrical body is provided with a rib-groove to receive a circular continuous resilient seal, which, when installed, bears against a PVC sewer pipe. This sealing between the PVC sewer pipe coupled with the grout sealing between the cylindrical body and the manhole, creates the overall sealing of the installed ABS manhole adapter. It is claimed that this coupling-collar serves well in making a connection between a pipe and a manhole. However, since the coupling-collar cannot be expanded or contracted, the sealing is by means of a friction fit or stab type joint, and by the effectiveness of the grouting used between the coupling-collar and designated hole in the manhole. Any relative movement between the manhole and pipe, such as through back filling or earth settlement, can easily damage the grouting and the effectiveness of the sealing provided thereby.
U.S. Pat. No. 4,478,437, to Skinner, represents another approach in providing a coupling between a pipe and a hole in the wall of a manhole. The invention thereof relates to a radially expandable locking sleeve which includes a cylindrical relatively stiff but resiliently flexible split strip of metal having opposed abuttably engageable ends. The sleeve is movable between two positions in which the end portions thereof may first be radially overlapped and secondly may be interlockingly engaged end-to-end. Means are provided for locking the end portions in end-to-end relation, such means including radially overlapped portions on each of the sleeve ends, which have outer peripheral surfaces that lie in and extend over an extended area substantially coincident with the outer cylindrical surface of the sleeve. The overlapped portions include abuttable portions which are both laterally and circumferentially engageable to hold the ends against lateral displacement and against circumferential movement toward each other. Further, the coupling device includes provision for the use of a tubular gasket of elastomeric material in combination with the expandable locking sleeve.
The device of Skinner, like that of Knappert et al., is not without its shortcomings. The elastomeric gasket, for example, is exposed to rocks, stones and other debris that can puncture and damage same during a backfilling operation. Further, a special hydraulic tool is required to expand the split sleeve from a first position to a second position. The patentee employs a hose type compression clamp about the pipe to be joined to the manhole. With obvious limits on how much force can be applied about the pipe, an effective seal is questionable.
The present invention avoids the problems of the prior art by the provision of an incrementally expandable and contractual coupling arrangement that provides effective sealing between the respective members to be coupled. The novel features of this invention will become apparent to those skilled in the art from a reading of the following specification, particularly when read in conjunction with the accompanying drawings.